I mean while it is a controversial diagnosis, some professionals believe in it so it's not impossible than a reputable doctor would determine someone has DID. And getting a second dissenting opinion, provided it is readily available, might actually hinder any actual treatment and create more confusion than be helpful (as it happens sometimes in physical medecine over some rare illnesses)
Mental health is the most complicated of things.
OniLinkPlus sounds like a textbook attention seeker though, no argument there. Not to say he doesn't need help, he sure does. Must be though for his family (since he mentioned being covered on health bills by per plan, at least he has that).